1. FIELD OF THE INVENTION
The present invention relates to diagnostic devices and, more particularly, to an improved test strip for blood glucose monitoring.
2. DESCRIPTION OF THE PRIOR ART
Blood glucose monitoring strips are known. Usually, such strips include an end grasped by the fingers and a single testing area at an opposite end, onto which a sample of blood is deposited, followed by a determination of the glucose level in the sample. Such prior art monitoring strips include but one testing area; if further testing is indicated, e.g., for confirmation purposes, then another entire monitoring strip must be used. This is both inconvenient and expensive.
The instant invention solves the problem by providing a blood glucose monitoring strip having at least two, serially arranged testing areas, divided conveniently by a tear off perforation line, for example, so that a subsequent test may be conducted without the need of acquiring an entire new monitoring strip. This arrangement provides numerous advantages as will be discussed in detail below.
Dry dip-and-read reagent strips for use in determining the concentration of glucose are, of course, well known. Continuous and accurate monitoring of the level of glucose in the blood is extremely important in the management of diabetes. Insulin and the amount of carbohydrate ingested control the level of glucose in the blood. If there is too little insulin present, the result is a very high glucose level. Conversely, if there is too much insulin present, then the glucose level will be unacceptably low. Either condition presents serious health consequences for the diabetic.
Furthermore, it is preferable to determine glucose levels directly from a blood sample rather than a urine sample. Urine glucose measurements are useful, but do not accurately confirm the level of glucose in the blood, because a urine glucose level is related directly to the level of glucose in the blood and the ability of the kidney to reabsorb glucose. So, in point of fact, a urine sample cannot tell a diabetic how low his glucose level is.
Commonly, the monitoring strips under discussion include a plastic strip with an absorbent paper piece impregnated with an enzyme system as well as a color indicator compound which changes color when oxidized. After the sample being tested is deposited onto the strip, the color formed on the strip is either machine read or compared with a color chart which is calibrated to represent various glucose concentrations. Several brands of such strips are available, including: the Lifescan strip, manufactured by Lifescan, Inc., Mountain View, Calif.; the Chemstrip bG strip, a trademarked product of Bio-Dynamic/Boehringer Mannheim Diagnostics, Inc.; and a strip sold under the trademark Dextrostix by Ames Company Division, Miles Laboratories, Inc. Further discussion of such strips can be found in the following enumerated patents, although these specific patents are directed to control solutions for such strips. These patents are: U.S. Pat. No. 3,920,580, issued Nov. 18, 1975 to Raymond L. Mast, and assigned to Miles Laboratories, Inc., Elkhart, Ind.; U.S. Pat. No. 4,729,959, issued Mar. 8, 1988 to Wayne L. Ryan, and assigned to Streck Laboratories, Inc. of Omaha, Nebr.; and U.S. Pat. No. 5,187,100, issued Feb. 16, 1993 to David P. Matzinger et al., and assigned to Lifescan, Inc., of Mountain View, Calif. This last mentioned patent will be discussed again hereinbelow.
There are other prior art teachings directed to testing strips or the like and including more than one testing area, but in each instance, the additional testing area or areas are provided for different tests or readings, and are employed simultaneously in conducting a test, rather than serially. For example, U.S. Pat. No. 4,275,031 issued Jun. 23, 1981 to Wolfgang Fischer et al., and assigned to Merck Patent Gesellschaft mit beschrankter Haftung of Darmstadt, Germany, shows a strip used in carrying out colorimetric or photometric determinations, and including spaced apart testing areas or reagent zones arranged one above another. However, these multiple zones are provided so that multiple analyses may be conducted simultaneously, rather than serially, the zones being identical so that the same test is again conducted, as is the case with the instant invention.
Similarly, the following six prior patent and published patent applications show testing devices with multiple zones or areas which are different from one another so that different analyses may be conducted simultaneously. None of these prior teachings is directed to testing strips with serially arranged, identical testing areas or zones for serially conducting precisely the same test, e.g., blood glucose determination. U.S. Pat. No. 5,183,742, issued Feb. 2, 1993 to Kouichi Omoto, et al., and assigned to Dai Nippon Insatsu Kabushiki of Kaisha, Japan teaches a testing device or strip having multiple, side by side or vertically arrayed detection regions or zones, but for simultaneous testing of a body fluid, so as to determine, for example, levels of glucose and protein and the pH of a sample. Another test device for the determination of glucose, the device including a strip with serially arranged zones, these being a measurement zone, a reaction zone, and a detection zone, is seen in U.K. Patent Application 2,026,160, published Jan. 30, 1980, and filed by VEB Arzneimittelwerk of Dresden, Germany. Again, the two disclosures just mentioned specifically teach a strip having different zones with different characteristics for the simultaneous testing of a sample, rather than serial testing of a sample with a strip having chemically identical testing zones or areas but employed serially, one after the other.
U.S. Pat. No. 4,981,786, issued Jan. 1, 1991 to Geoffrey A. Dafforn et al., and assigned to Syntex (U.S.A.) Inc., of Palo Alto, California teaches a multiple port assay device wherein a sample is introduced through a first port to a liquid absorbing zone, and a liquid reagent other than the sample is introduced through a second port to the liquid absorbing zone. Again, serial, identical testing employing a strip with chemically identical testing zones is not taught or suggested.
The following two patent are directed to fecal occult blood specimens and assay techniques. Each discloses a sampling device with at least two fecal matter smear areas for receiving a sample; serial testing with chemically identical areas is neither taught or suggested. The two patent are U.S. Patent No's. 5,100,619, issued Mar. 31, 1992 to Josefina T. Baker et al., and assigned to Beckman Instruments, Inc., of Fullerton, Calif., and U.S. Pat. No. 5,182,191, issued Jan. 26, 1993, to Eugene Fan et al., and assigned to Pacific Biotech, Inc., of San Diego, Calif.
Published European patent application No. 0 369 836, filed by Institut Textile de France and published May 23, 1990, teaches yet another testing device with multiple test areas or zones for conducting different tests on the same sample. Again, the structure and use of a strip having chemically identical zones for serial testing is not seen in this reference.
Accordingly, none of the above inventions and patents, taken either singly or in combination, is seen to describe the instant invention as claimed.